N-acetylcysteine compositions and methods for the treatment and prevention of drug toxicity

ABSTRACT

The invention provides pharmaceutical compositions for the treatment or prevention of the toxic effects of therapeutic agents and methods of treating or preventing such toxicity using a toxicity reducing amount of N-acetylcysteine either alone or in combination with a therapeutically effective amount or, to achieve its therapeutic advantages, an amount larger than what is customarily given as a therapeutically effective amount, of a therapeutic agent. The invention also provides pharmaceutical compositions for the treatment or prevention of the toxic effects of therapeutic agents and methods of treating or preventing such toxicity using a toxicity reducing amount of N-acetylcysteine either alone or in combination with a therapeutically effective amount or, to achieve its therapeutic advantages, an amount larger than what is customarily given as a therapeutically effective amount, of a therapeutic agent whose side effects are made worse by increased oxidative stress or treatment related decreases in subject cysteine/glutathione levels or are otherwise relieved by administration of NAC.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Patent Application No.60/280,600, filed Mar. 30, 2001 the contents of which are incorporatedby reference herein.

GOVERNMENT SUPPORT

This work is supported at least in part by grants from the N.I.H.CA42509-14. The government may have certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to compositions for the treatment orprevention of drug toxicity in mammals including humans which may resultfrom the administration of therapeutic agents and to methods of treatingor preventing such toxicity. The compositions of this invention comprisea toxicity-reducing amount of N-acetylcysteine (NAC) alone or incombination with a therapeutically effective amount or, to achieve itstherapeutic advantages, an amount larger than what is customarily givenas a therapeutically effective amount, of a therapeutic agent,preferably in combination with a pharmaceutically acceptable carrier.The method of treating or preventing drug toxicity in humans comprisesadministering a toxicity-reducing amount of NAC alone or in combinationwith a therapeutically effective amount or, to achieve its therapeuticadvantages, an amount larger than what is customarily given as atherapeutically effective amount, of a therapeutic agent, preferably incombination with a pharmaceutically acceptable carrier.

BACKGROUND OF THE INVENTION

Glutathione (GSH), a tripeptide that is normally found in all animalcells and most plants and bacteria at relatively high (1-10 millimolar)concentrations, helps to protect cells against oxidative damage thatwould otherwise be caused by free radicals and reactive oxidativeintermediates (ROIs) produced during cell metabolism or as the resultsof, for example, drug overdose. Glutathione is itself the majorscavenger of reactive oxidative intermediates present in all eukaryoticforms of life and is generally required to protect cells against damageby oxidants. Glutathione reduces (and thereby detoxifies) intracellularoxidants and is consumed by this reaction. Glutathione is oxidized tothe disulfide linked dimer (GSSG), which is actively pumped out of cellsand becomes largely unavailable for reconversion to reduced glutathione.Thus, unless glutathione is resynthesized through other pathways,utilization of this compound is associated with a reduction in theamount of glutathione available. The antioxidant effects of glutathioneare also mediated less directly by the role of this compound inmaintaining other antioxidants in reduced form. Thus, pharmaceuticalcompounds that replenish or elevate glutathione levels work, at least inpart, through enhancement of the defense mechanisms seemingly utilizedto normally protect tissue from ROI mediated damage.

Glutathione depletion has been implicated in the pathology of a numberof diseases including infection by human immunodeficiency virus (HIV).In HIV infection, cysteine/glutathione depletion is known to impairT-cell function and is associated with impaired survival of subjectswith less than 200 CD4 T-cells per μl blood.

Drug toxicity is a very widespread problem. Cysteine/glutathionedepletion and oxidative stress (See U.S. Pat. No. 4,757,063) intensifydrug toxicity effects and have been implicated in the mechanism of drugtoxicity reactions.

For example, acetaminophen is known to act to depletecysteine/glutathione and cause a variety of drug toxicity symptoms.Acetaminophen, also known as paracetamol and N-acetyl-p-aminophenol, isone of the most widely used pharmaceutical analgesic and antipyreticagents in the world. It is contained in over 100 products and iscommonly found in the U.S. as immediate release tablets and asextended-release preparations. Various children's chewable, suspension,and elixir formulations that contain acetaminophen are prevalent.Acetaminophen is also found as a component of combination drugs, such aspropoxyphene/acetaminophen and oxycodone/acetaminophen.

Acetaminophen continues to be the most commonly encountered substance intoxic ingestions. In many cases, acetaminophen overdoses areunintentional and are undiagnosed until after substantial damage hasalready occurred. Repeated administration of acceptable size doses ofacetaminophen can produce toxicity symptoms. As discussed by Donovan(1999) Academic Emergency Med. 6:1079-1082, methods for detectingpost-ingestion blood levels of acetaminophen suffer from poor predictivevalues. Even in the simple case of a single acute ingestion, patientswith no discernible risk factors for liver injury and low blood levelsof acetaminophen still develop toxicity and even die.

Many companies package acetaminophen under different trade names,resulting in inadvertent overdosing by less sophisticated patients andparents who do not read the information on the packaging. In addition,cold remedies and other over-the-counter preparations often containacetaminophen, which is listed among a series of generic drug names thatare difficult for patients and parents to read. Therefore, patientsoften are unaware of the amount of acetaminophen that they havereceived. Children are especially vulnerable to accidental exposure dueto their smaller size, the presence of acetaminophen in multipleover-the-counter remedies, and a reluctance to administer aspirin andother NSAIDs to children for fever due to the risk of Reye's Syndromeand renal tubular injury. The antipyretic value of acetaminophen clearlyhas been demonstrated and hence acetaminophen is widely used inhospitals for this purpose. However, acetaminophen may not be theantipyretic agent of choice under circumstances where renal or hepaticfunction is in danger of being compromised.

It is well established that large acetaminophen overdose causeshepatotoxicity and, in some cases, nephrotoxicity in humans and inexperimental animals. Acute overdosage of acetaminophen results indose-dependent and potentially fatal hepatic necrosis as well as (inrare cases) renal tubular necrosis and hypoglycemia. Acetaminophen israpidly absorbed from the stomach and small intestine and is normallymetabolized by conjugation in the liver to nontoxic agents, which arethen eliminated in the urine. In acute overdoses, or when maximum dailydoses are exceeded over a prolonged period, the normal pathways ofmetabolism become saturated.

Excess acetaminophen is metabolized in the liver via the mixed functionoxidase P450 system to a toxic, N-acetyl-p-benzoquinone-Imine (NAPQI).NAPQI has an extremely short half-life and is rapidly conjugated withglutathione, a sulfhydryl donor, and removed from the system. Underconditions of excessive NAPQI formation or reduced glutathione stores,NAPQI is free to bind to vital proteins and the lipid bilayer ofhepatocytes. This results in hepatocellular death and subsequentcentrilobular liver necrosis. Immumunohistochemical studies havesuggested that NAPQI-protein adducts appear even at sub-hepatotoxicacetaminophen doses and before depletion of total hepatic glutathionewhich may be related to rare cases of hypersensitivity. In addition,decreased intracellular cysteine/glutathione can contribute to celldeath via mechanisms that do not involve NAPQI.

The direct cost of acetaminophen overdose has been estimated to be $87million annually. Effective protocols have been developed and tested tostratify risk and treat patients who present soon after a single largedose of acetaminophen. However, many patients present after a delay longenough to metabolize all the acetaminophen, after two or more ingestionsover several hours, or after several days of excessive self-medication.Under these circumstances it is difficult for the clinician to estimatethe risk of adverse outcome before hepatic or renal injury occurs. See,for example, Bond and Hite (1999) Acad. Emerg. Med. 6:1115-1120; andDonovan (1999) Acad. Emerg. Med. 6:1079-1082. However, early treatmentof acetaminophen overdosage is considered to be crucial, and vigoroussupportive therapy is essential when intoxication is severe.

Nucleoside reverse transcriptase inhibitors (NRTIs), of which thepyrimidine nucleoside analogue azidothymidine (AZT, zidovudine), is acommon example, are often given in combination therapies with otheranti-retroviral drugs to treat HIV. Long-term therapy with AZT iscommonly associated with dose-dependent hematologic toxicity whichmanifests as low erythrocyte counts and elevated mean red cell volume,and with muscle fiber toxicity, particularly in patients with advancedHIV disease. Some studies indicate that AZT's toxic interactions resultfrom the generation of reactive oxygen species (ROIs) that react withand deplete intracellular glutathione levels. See de la Asuncion, et al(1998) J. Clin. Invest. 102(1): 4-9; Gogu et al. (1991) Exp. Hematol.19(7): 649-652; Gogu and Agrawal (1996) Life Sci. 59 (16): 1323-1329;Prakash et al (1997) Arch. Biochem. Biophys. 343 (2): 173-80.

Results have shown that acetaminophen usage, which lowers glutathionelevels exacerbates AZT toxicity. Richman, et al. (1987) N. Eng. J. Med.317: 192-97. De Rosa et al. recently have shown that treatment with NACwhich increases glutathione levels decreases the toxicity. De Rosa etal., submitted to JAMA for publication.

Evidence from in vitro and animal studies supports this conclusion. AZTtreatment caused oxidative damage to mitochondrial DNA (includingincreased mitochondrial lipoperoxidation) and increased levels ofoxidized glutathione in skeletal muscle in mice. See de la Asuncion, etal. (1998) J. Clin. Invest. 102(1): 4-9. NAC and the anti-oxidantVitamins C and E have been shown to prevent this AZT-induced toxicity.See id.; Gogu, et al (1991) Exp. Hematol. 19, 649-52; and Gogu andAgrawal (1996) Life Chem. Rep. 4, 1-35. Furthermore, AZT treatmentintensifies glutathione depletion in HIV-TAT transgenic mice (seePrakash, O., et al. Arch. Biochem. Biophys. (1997) 343: 173-80) whereexpression of the TAT protein has been shown to deplete glutathione bydecreasing glutathione biosynthesis (see Choi, J., et al., (2000) J.Biol. Chem. 275 (5): 3693-98) and the activity of antioxidant enzymes(Flores et al. (1993) Proc. Nat. Acad. Sci. 90 (16): 7632-36). Studieswith TAT-transgenic mice also show that AZT toxicity is enhanced in thisglutathione-depleted environment. See Prakash et al. (1997) Arch.Biochem. Biophys. 343, 173-80.

Early clinical trials of AZT efficacy in HIV disease revealed anassociation between AZT toxicity and the use of acetaminophen. See,e.g., Richman, et al. (1987) New Eng. J. Med. 317(4): 192-97. Althoughthe mechanism of this toxic reaction is not fully understood,acetaminophen does not impair AZT detoxification since no difference inAZT's rate of destruction has been observed. Since acetaminophen isknown to deplete glutathione, the potentially harmful effect ofco-administering acetaminophen and AZT appears to be mediated throughglutathione depletion. Thus, in conditions where glutathione already isdepleted, such as in later stages of HIV disease, detoxification ofacetaminophen (which can be expected to further deplete glutathionestores in the liver and elsewhere) would increase the potential for AZTtoxicity.

Long-term antibiotic usage also often produces drug toxicity reactions.Toxicity reactions for a given antibiotic are a function of itsmechanism of action and the pathway(s) by which it is metabolicallydegraded.

Scientists have long sought to identify agents that will be generallyeffective in combating drug toxicity reactions. Protective agents fordrug overdose have been extensively studied. A known method of treatmentfor acetaminophen overdose is the administration of sulfhydrylcompounds. L-methionine, L-cysteine, and either the purifiedL-enantiomer or the racemate mixture of N-acetylcysteine are known tohave a protective action in animals. Methionine and another sulfhydrylcompound, cysteamine, have been reported to provide some protection.Also, cimetidine, dimethyl sulfoxide, and ethanol have been shown toinhibit acetaminophen bioactivation. N-acetylcysteine has been shown tobe effective in humans when given orally. Early administration ofcompounds supplying sulfhydryl groups (0 to 10 hours after acetaminopheningestion) may prevent or minimize hepatic and renal injury in cases ofacetaminophen overdose. NAC is now used by many physicians for treatmentof hepatic failure of any etiology, whether known or unknown, and is theaccepted antidote for cyclophosphamide poisoning. NAC also is used toprevent toxicity due to radiation therapy contrast material in patientsundergoing such treatment. The mechanisms through which NAC prevents orreverses toxicity are mainly thought to involve glutathionereplenishment. However, additional mechanisms through which NAC worksdirectly via the cysteine molecule itself are not excluded.

Recently we have shown that treatment with NAC decreases AZT'shematologic toxicity in subjects taking AZT. It appears that NACprovides cysteine needed to redress the excessive sulfur loss thatoccurs in HIV disease and specifically to replenish intracellularglutathione. This in turn helps to restore the reducing power necessaryfor deoxynucleotide synthesis and to bring the size of thedeoxynucleotide pool, and hence the rate of cell division, back intonormal range. This decreases the AZT-mediated inhibition of erythroiddevelopment, helps to improve the overall metabolism and stability oferythrocytes and their progenitors (for example, by enabling optimalfunctioning of the glucose-6-phosphate dehydrogenase and otherenergy-supplying pathways). In addition, it improves the cell's abilityto withstand the production of oxidants induced by the introduction ofdrugs (such as AZT) and the internal production of molecules (such asTNF and HIV-TAT) that trigger intracellular oxidant production.

Improved formulations and methods to prevent drug toxicity reactionsduring long term therapy are of particular interest in view of theconsiderable loss of life attributable to, and cost of treatment of,such reactions. The present invention addresses this problem.

SUMMARY OF THE INVENTION

Pharmaceutical compositions and methods of treatment are provided forserial or co-administration of NAC with any therapeutic agent todecrease drug toxicity, including those drugs whose side effects aremade worse by decreases in subject intracellular cysteine/gluathionelevels or increased oxidative stress, or whose side effects areotherwise relieved by administration of NAC. The serial orco-administration of NAC makes a therapeutic agent safer at currentlyrecognized standard therapeutic doses and allows increased doses of thattherapeutic agent to be administered for its beneficial purposes withouttoxic side effects.

According to one embodiment of the invention, compositions useful fortreating or preventing the toxic effects of therapeutic agents inmammals are provided comprising a toxicity-reducing amount ofN-acetylcysteine or a pharmaceutically acceptable salt or derivativethereof alone or in combination with a therapeutic or greater amount ofa therapeutic agent, in combination with a pharmaceutically acceptableexcipient or carrier. In another embodiment, such compositions compriseat least about 1 mg N-acetylcysteine or a pharmaceutically-acceptablesalt or derivative thereof. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein the therapeutic agent is at least oneantibiotic or antiviral agent. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein the therapeutic agent is at least oneantibiotic or antiviral agent that produces oxidative stress. In anotherembodiment, such compositions comprise a therapeutic amount of atherapeutic agent in combination with a toxicity-reducing amount of NACor a pharmaceutically acceptable salt or derivative thereof, wherein thetherapeutic agent is at least one antibiotic or antiviral agent thatproduces treatment-related decreases in subject cysteine/glutathionelevels. In another embodiment, such compositions comprise a therapeuticamount of a therapeutic agent in combination with a toxicity-reducingamount of NAC or a pharmaceutically acceptable salt or derivativethereof, wherein the therapeutic agent is an analgesic, antipyretic orother therapeutic compound. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein the therapeutic agent is an analgesic,antipyretic or other therapeutic compound that produces oxidativestress. In another embodiment, such compositions comprise a therapeuticamount of a therapeutic agent in combination with a toxicity-reducingamount of NAC or a pharmaceutically acceptable salt or derivativethereof, wherein the therapeutic agent is an analgesic, antipyretic orother therapeutic compound that produces treatment-related decreases insubject cysteine/glutathione levels. In another embodiment, suchcompositions comprise a therapeutic amount of a therapeutic agent incombination with a toxicity-reducing amount of NAC or a pharmaceuticallyacceptable salt or derivative thereof, wherein the compound is aparaminophenol derivative, which includes phenacetin and its activemetabolite acetaminophen. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein each dosage unit contains a standard doseof acetaminophen and at least about 1 mg of NAC. In another embodiment,such compositions comprise a therapeutic amount of a therapeutic agentin combination with a toxicity-reducing amount of NAC or apharmaceutically acceptable salt or derivative thereof, wherein thetherapeutic agent is an anti-retroviral agent. In another embodiment,such compositions comprise a therapeutically effective amount of AZT incombination with a toxicity-reducing amount of NAC to decrease keyaspects of AZT toxicity in human HIV patients, e.g., macrocytic anemia.

In another embodiment, a method of treating or preventing the toxiceffects of therapeutic agents in mammals comprises administering atoxicity reducing amount of NAC or a pharmaceutically acceptable salt orderivative thereof, alone or in combination with a normal dosage or agreater than normal dosage of a therapeutic agent, in combination with apharmaceutically acceptable carrier. In another embodiment, the methodcomprises administering at least about 1 mg NAC or a pharmaceuticallyacceptable salt or derivative thereof to a patient receiving nutritionparenterally. In another embodiment, the method comprises administeringa therapeutic amount of at least one antibiotic or antiviral agent incombination with NAC or a pharmaceutically acceptable salt or derivativethereof. In another embodiment, the method comprises administering atherapeutic amount of at least one antibiotic or antiviral agent incombination with NAC or a pharmaceutically acceptable salt or derivativethereof wherein the antibiotic or antiviral agent produces oxidativestress. In another embodiment, the method comprises administering atherapeutic amount of at least one antibiotic or antiviral agent incombination with a toxicity-reducing amount of NAC or a pharmaceuticallyacceptable salt or derivative thereof, wherein the antibiotic orantiviral agent produces treatment-related decreases in subjectcysteine/glutathione levels. In another embodiment, the method comprisesadministering a therapeutic amount of an anti-retroviral agent incombination with a toxicity reducing amount of NAC. In anotherembodiment, the method comprises administering a therapeutic amount ofan anti-retroviral agent in combination with a toxicity-reducing amountof NAC wherein the anti-retroviral agent is AZT. In another embodiment,the method comprises administering a therapeutic amount of AZT seriallyor in combination with a toxicity-reducing amount of NAC perinatally. Inanother embodiment, the method comprises administering a therapeuticamount of AZT serially or in combination with a toxicity-reducing amountof NAC neonatally. In another embodiment, the method comprisesadministering a therapeutic amount of AZT for suspected or knownexposure to the HIV virus serially or in combination with atoxicity-reducing amount of NAC. In another embodiment, the methodcomprises administering a therapeutic amount of at least one analgesic,antipyretic or other therapeutic compound in combination with a toxicityreducing amount of NAC or a pharmaceutically acceptable salt orderivative thereof. In another embodiment, the method comprisesadministering a therapeutic amount of at least one analgesic,antipyretic or other therapeutic compound in combination with atoxicity-reducing amount of NAC, wherein the compound produces oxidativestress. In another embodiment, the method comprises administering atherapeutic amount of at least one analgesic, antipyretic or othertherapeutic compound in combination with a toxicity-reducing amount ofNAC, wherein the compound produces treatment-related decreases insubject cysteine/glutathione levels. In another embodiment, the methodcomprises administering a therapeutic amount of at least one analgesic,antipyretic or other therapeutic compound in combination with atoxicity-reducing amount of NAC wherein the compound is a paraminophenolderivative, which includes phenacetin and its active metaboliteacetaminophen. In another embodiment, the method comprises administeringa therapeutic amount of acetaminophen in a standard dosage serially orin combination with at least about 1 mg per dose N-acetylcysteine totreat a fever or pain in a patient who responds normally toacetaminophen. In another embodiment, the method comprises administeringa greater than standard dosage of acetaminophen serially or incombination with at least about 4 mg/kg N-acetylcysteine to treat afever nonresponsive to the standard dose of acetaminophen. In anotherembodiment, the method comprises administering a standard dosage ofacetaminophen serially or in combination with at least about 1 mg perdose N-acetylcysteine to treat patients who require acetaminophen duringtheir exposure to radiation contrast agents.

The combined compositions and methods provide protection against toxicdrug reactions, particularly where overdosing may be inadvertent,undiagnosable, or even therapeutically desirable if the toxic sideeffects could be removed.

DETAILED DESCRIPTION OF THE INVENTION

The invention described herein provides for the serial orco-administration of any therapeutically active agent with NAC torelieve the toxic effects of such therapy in mammals including wheretoxic effects of such therapy in mammals may be due to oxidative stressor treatment-related decreases in subject cysteine/glutathione levels orare otherwise relieved by administration of NAC.

The pharmaceutical compositions and methods of treatment above describedinclude providing the pharmaceutical compositions in oral, parenteral orsuppository form for oral, parenteral or rectal administration. It ispreferred that the NAC be substantially free of sulfones or otherchemicals that interfere with the metabolism of the co-administereddrug, e.g., acetaminophen, in its bioactive form. It is also preferredthat the NAC be substantially free of its oxidized form,di-n-acetylcysteine. It is preferred that the therapeutic agent,serially or co-administered, be in any form in which it is typicallyavailable and the composition should be prepared in a manner thatsubstantially prevents oxidation of the NAC during preparation orstorage.

In one aspect of the invention, the combined formulation is administeredto individuals having an increased susceptibility for acetaminophentoxicity. With regard to acetaminophen toxicity in adults,hepatotoxicity may occur after ingestion of a single dose of more thanabout 7.5 to 10 g of acetaminophen. However, alcoholics and individualstaking isoniazid have elevated P-450 2E1 levels and can have increasedsusceptibility for acetaminophen toxicity. The risk of hepatotoxicitywith single or serial doses of acetaminophen may also be increased inpatients regularly taking other hepatic enzyme-inducing agents,especially barbiturates or other anticonvulsants. In addition,individuals taking classes of antibiotics that reduce GSH, includingsulfas, chloramphenicol, macrolides and fluoroquinolones, may haveincreased risk of hepatotoxicity with acetaminophen. Also, although mostacetaminophen is metabolized through the glucoronidation pathway inadults, some is converted to a reactive intermediate that is detoxifiedin a GSH-dependent reaction. See Thomas, S. H. (1993) Pharmacol. Ther.60: 91-120. Pre-adolescent children, particularly below school age, lackthe normal glucoronidation pathway and rely to a greater degree thanadults on GSH for detoxification of acetaminophen, increasing theirsusceptibility to acetaminophen-induced-toxicity. Further, patientsreceiving parenteral nutrition who may not receive an adequate dietarysource of cysteine or whose condition may result in oxidative stresswill have an increased susceptibility to acetaminophen toxicity.Increased susceptibility can also result from a predisposition to GSHdeficiency, due to HIV and other infections, metabolic diseases, e.g.,diabetes, chronic diseases, sepsis, hepatic insufficiency and otherphysiologic oxidative stress.

With respect to acetaminophen, the formulations of the present inventionfind use as anti-pyretic and analgesic agents, and are suitable formedical indications treatable with acetaminophen alone. An improvementin product safety is provided by the inclusion of NAC, whichsubstantially prevents the possibility of accidental or inadvertentoverdosage. The combined use of acetaminophen and NAC enhances thedesired effects of acetaminophen while preventing its side effects, e.g.administering acetaminophen with NAC can allow acetaminophen dosing athigher levels, which would otherwise carry an unacceptable risk oftoxicity. The co-formulation with NAC can enhance the safety ofacetaminophen administration in severe illness and hence decreasepatient morbidity and mortality due to acetaminophen-induced hepatic andrenal injury. NAC administration may provide an additional benefit sinceit tends to reduce the negative effects of tumor necrosis factor alpha(TNF-α) and similar-acting cytokines.

NAC replenishes glutathione following acetaminophen overdose, whichotherwise leads to a fatal depletion of glutathione in the liver. Thisnon-toxic drug enters cells readily and replenishes the intracellularcysteine required to produce glutathione, thus leading to an increase inglutathione levels. It is important to note that NAC does not interferewith the peripheral action of acetaminophen as an analgesic oranti-pyretic, and thus its presence in the combined formulations of theinvention does not decrease the potency of the therapeutic agent. It maybe noted that the effectiveness of NAC depends on the presence of thereduced form, which may, for example, liberate the reduced form ofglutathione from homo- and hetero-disulfide derivatives inthiol-disulfide exchange reactions. The unit dose of acetaminophen inthe provided formulation may be higher than the conventional dose in theabsence of NAC. A typical unit dosage may be a solution suitable fororal or intravenous administration; an effervescent tablet suitable fordissolving in water, fruit juice, or carbonated beverage andadministered orally; a tablet taken from two to six times daily, or onetime-release capsule or tablet taken once or twice a day and containinga proportionally higher content of active ingredient, etc. Thetime-release effect may be obtained by capsule materials that dissolveat different pH values, by capsules that release slowly by osmoticpressure, or by any other known means of controlled release. Unit dosageforms may be provided wherein each dosage unit, for example,teaspoonful, tablespoonful, gel capsule, tablet or suppository, containsa predetermined amount of the compositions of the present invention.Similarly, unit dosage forms for injection or intravenous administrationmay comprise the compound of the present invention in a composition as asolution in sterile water, normal saline or another pharmaceuticallyacceptable carrier. The specifications for the unit dosage forms of thepresent invention depend on the effect to be achieved and the intendedrecipient.

It is preferred that the pharmaceutical compositions according to thepresent invention contained from about 80 mg to about 2000 mg ofacetaminophen per dosage unit, particularly from about 650 mg to about2000 mg per dosage unit. The amount of NAC per dosage unit is preferablyfrom 1 mg to 25000 mg, preferably at least 3 mg to 2,000 mg per dosageunit for oral administration, and 20-20,000 mg for parenteral.

The acetaminophen present in orally administrable solid unit doses willusually be at least about 80 mg (for pediatric doses), 325 mg, 500 mgand 650 mg, and may be as high as about 2000 mg, more usually not morethan about 1500 mg together with effective amounts of NAC. Suppositoriesare formulated in the manner well known in the art and usually compriseat least about 120 mg, 125 mg, 325 mg, 500 mg and 650 mg acetaminophenper dosage unit and may be as high as about 2000 mg, more usually notmore than about 1500 mg together with effective amounts of NAC. Oralliquid dosage forms usually comprise at least about 100 mg/ml, 120mg/2.5 ml, 120mg/5 ml, 160 mg/5 ml, 165 mg/5 ml, 325 mg/5 mlacetaminophen, and may be as high as about 2000 mg, more usually notmore than about 1500 mg together with effective amounts of NAC.

The unit dose of NAC, in combination with any one of the above doses ofacetaminophen, or alone for the treatment of acute hepatic injury in theabsence of toxic levels of acetaminophen, will usually comprise at leastabout 1.5 mg/kg to a maximum amount of 70 mg/kg (for pediatric doses),usually at least about 500 mg (for adult doses); and usually not morethan about 2,000 mg at the physician's discretion. Patients on therapyknown to deplete cysteine/glutathione or produce oxidative stress maybenefit from higher amounts of NAC.

Over-the-counter NAC can be variably produced and packaged. Because theproduction and packaging methods generally do not guard againstoxidation, the NAC can be significantly contaminated with bioactiveoxidation products. These may be particularly important in view of dataindicating that the oxidized form of NAC has effects counter to thosereported for NAC and is bioactive at doses roughly 10-100 fold less thanNAC (see Samstrand et al (1999) J. Pharmacol. Exp. Ther. 288: 1174-84).

The distribution of the oxidation states of NAC as a thiol and disulfidedepends on the oxidation/reduction potential. The half-cell potentialobtained for the NAC thiol/disulfide pair is about +63 mV, indicative ofits strong reducing activity among natural compounds (see Noszal et al.(2000) J. Med. Chem. 43:2176-2182). In a preferred embodiment of theinvention, the preparation and storage of the formulation is performedin such a way that the reduced form of NAC is the primary formadministered to the patient. Maintaining NAC containing formulations insolid form is preferable for this purpose. When in solution, NACcontaining formulations are preferably stored in a brown bottle that isvacuum sealed. Storage in cool dark environments is also preferred.

The determination of reduced and oxidized species present in a samplemay be determined by various methods known in the art, for example withcapillary electrophoresis, HPLC, etc. as described by Chassaing et al.(1999) J Chromatogr B Biomed Sci Appl 735(2):219-27.

The compositions of the present invention may be administered orally,parenterally, or rectally in dosage unit formulations containingconventional nontoxic pharmaceutically acceptable carriers, adjuvants,and vehicles as desired. The term parenteral as used herein includessubcutaneous injections, intravenous, intramuscular, intrasternalinjection, or infusion techniques. Topical administration may alsoinvolve the use of transdermal administration such as transdermalpatches or iontophoresis devices which are prepared according totechniques and procedures well known in the art.

Solid dosage forms for oral administration may include capsules,tablets, pills, powders, granules and gels. In such solid dosage forms,the active compounds may be admixed with at least one inert diluent suchas sucrose, lactose or starch. Such dosage forms may also comprise, asin normal practice, additional substances other than inert diluents,e.g., lubricating agents such as magnesium stearate. In the case ofcapsules, tablets, and pills, the dosage forms may also comprisebuffering agents. Tablets and pills can additionally be prepared withenteric coatings.

Suppositories for rectal administration of the drug composition, such asfor treating pediatric fever etc., can be prepared by mixing the drugwith a suitable nonirritating excipient such as cocoa butter andpolyethylene glycols which are solid at ordinary temperatures but liquidat the rectal temperature and will therefore melt in the rectum andrelease the drug.

Injectable preparations, for example, sterile injectable aqueous oroleaginous suspensions, may be formulated according to the known artusing suitable dispersing or wetting agents and suspending agents. Thesterile injectable preparation may also be a sterile injectable solutionor suspension in a nontoxic parenterally acceptable diluent or solvent,for example, as a solution in 1, 3-butanediol. Among the acceptablevehicles and solvents that may be employed are water, Ringer's solution,and isotonic sodium chloride solution. In addition, sterile, fixed oilsare conventionally employed as a solvent or suspending medium.

The compositions of this invention can further include conventionalexcipients, i.e., pharmaceutically acceptable organic or inorganiccarrier substances suitable for parenteral application which do notdeleteriously react with the active compounds. Suitable pharmaceuticallyacceptable carriers include, but are not limited to, water, saltsolutions, alcohol, vegetable oils, polyethylene glycols, gelatin,lactose, amylose, magnesium stearate, talc, silicic acid, viscousparaffin, perfume oil; fatty acid monoglycerides and diglycerides,petroethral fatty acid esters, hydroxymethylcellulose,polyvinylpyrrolidone, etc. The pharmaceutical preparations can besterilized and if desired, mixed with auxiliary agents, e.g.,lubricants, preservatives, stabilizers, wetting agents, emulsifiers,salts for influencing osmotic pressure, buffers, colorings, flavoringand/or aromatic substances and the like which do not deleteriously reactwith the active compounds. For parenteral application, particularlysuitable vehicles consist of solutions, preferably oily or aqueoussolutions, as well as suspensions, emulsions, or implants. Aqueoussuspensions may contain substances which increase the viscosity of thesuspension and include, for example, sodium carboxymethyl cellulose,sorbitol and/or dextran. Optionally, the suspension may also containstabilizers.

The composition, if desired, can also contain minor amounts of wettingor emulsifying agents or pH buffering agents. The composition can be aliquid solution, suspension, emulsion, tablet, pill, capsule, sustainedrelease formulation, or powder. The composition can be formulated as asuppository, with traditional binders and carriers such astriglycerides. Oral formulations can include standard carriers such aspharmaceutical grades of mannitol, lactose, starch, magnesium stearate,sodium saccharine, cellulose, magnesium carbonate, etc.

The therapeutically active agent of the present invention can beformulated per se or in salt form. Pharmaceutically acceptable saltsinclude, but are not limited to, those formed with free amino groupssuch as those derived from hydrochloric, phosphoric, sulfuric, acetic,oxalic, tartaric acids, etc., and those formed with free carboxyl groupssuch as those derived from sodium, potassium, ammonium, calcium, ferrichydroxides, isopropylamine, triethylamine, 2-ethylamino ethanol,histidine, procaine, etc.

The amount of compounds in the compositions of the present inventionwhich will be effective in the treatment of a particular disorder orcondition will depend on the nature of the disorder or condition, andcan be determined by standard clinical techniques. See, for example,Goodman and Gilman; The Physician's Desk Reference, Medical EconomicsCompany, Inc., Oradell, N.J., 1995; and to Drug Facts and Comparisons,Facts and Comparisons, Inc., St. Louis, Mo., 1993. As the addition ofNAC does not affect the therapeutic efficacy of acetaminophen, it isgenerally not necessary to adjust the dosage from what would ordinarilybe administered for acetaminophen alone, and in fact the dose may beraised due to the increased safety of the present formulations. Theprecise dose to be employed in the formulation will also depend on theroute of administration, and the seriousness of the disease or disorder,and should be decided according to the judgment of the practitioner andeach patient's circumstances.

The present invention also provides a pharmaceutical pack or kitcomprising one or more containers filled with one or more of theingredients of the pharmaceutical compositions of the invention.Associated with such container(s) can be a notice in the form prescribedby a governmental agency regulating the manufacture, use or sale ofpharmaceuticals or biological products, which notice reflects approvalby the agency of manufacture, use or sale for human administration.

In another embodiment of the invention, formulations of NAC are providedfor the treatment of acute hepatic failure of unknown etiology, forexample for the treatment of acetaminophen or other drug toxicity wherethe serum levels of the toxic drug indicate non-toxic levels where theremay be an increased risk for toxicity due to oxidative stress or otheraspects of the patient's condition. The NAC formulations for treatmentof such patients will utilize a formulation as described above.

Many such patients having severe hepatic failure also have serum levelsof acetaminophen within the accepted non-toxic range, due to variousfactors. Such factors may include the lapsed time before presentation ofthe toxic effects, for example in incidences of intentional overdose.

Inadvertent acetaminophen toxicity has also been reported with normallyaccepted dosing regimens when associated with certain viral infections,toxic exposure, and drug use, such as sulfa, chloramphenicol anderythromycin. Many of these patients present with non-toxicacetaminophen levels, but toxicity still results from oxidative stressand other drug-related effects on hepatocytes.

Another group of patients are under oxidative stress or otherwise havesevere illness that makes them more susceptible than normal toacetaminophen toxicity. Such patients may include, for example, patientswith septic shock, distributive shock, hemorrhagic shock, acuterespiratory distress syndrome, organ failure, and closed head injury.Patients in this group are routinely treated with acetaminophen as ananti-pyretic and mild analgesic, which may inadvertently result insevere hepatic or renal damage.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the invention. The upper and lowerlimits of these smaller ranges which may independently be included inthe smaller ranges is also encompassed within the invention, subject toany specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either bothof those included limits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present invention, the preferredmethods and materials are now described. All publications mentionedherein are incorporated herein by reference to disclose and describe themethods and/or materials in connection with which the publications arecited.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “and”, and “the” include plural referents unless thecontext clearly dictates otherwise. All technical and scientific termsused herein have the same meaning.

The publications discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the present invention, and are not intended to limit thescope of what the inventors regard as their invention nor are theyintended to represent that the experiments below are all or the onlyexperiments performed. We present AZT and acetaminophen as examples ofthe model for toxicity we propose. Efforts have been made to ensureaccuracy with respect to numbers used (e.g. amounts, temperature, etc.)but some experimental errors and deviations should be accounted for.Unless indicated otherwise, parts are parts by weight, molecular weightis weight average molecular weight, temperature is in degreesCentigrade, and pressure is at or near atmospheric.

Example 1

A child or adult having a fever can be treated with a formulationcomprising 15 mg/kg acetaminophen and 1 mg/kg of either the purifiedL-enantiomer or the racemate mixture composed of equal proportions ofthe D- and L-isomers of NAC administered either serially orco-administered three or four times a day up to the highest tolerabledose, given that there will be individual variability in the ability totolerate NAC. The dose of NAC may vary from 0.03 to four times theamount of acetaminophen taken.

Example 2

A child or adult having a fever that does not respond to acetaminophenat a standard dose level can be treated with a formulation comprising15-50 mg/kg acetaminophen and 3-130 mg/kg of either the purifiedL-enantiomer or the racemate mixture composed of equal proportions ofthe D- and L-isomers of NAC administered either serially orco-administered three or four times a day up to the highest tolerabledose, given that there will be individual variability in the ability totolerate NAC.

Example 3

A normally healthy child or adult having a low fever can be treated forseveral days at normal acetaminophen dosage levels with a formulationcomprising 80 mg per tablet acetaminophen and 3 mg per tablet of eitherthe purified L-enantiomer or the racemate mixture composed of equalproportions of the D- and L-isomers of NAC administered either seriallyor co-administered three or four times a day up to the highest tolerabledose, given that there will be individual variability in the ability totolerate NAC, the number of tablets to vary according to the patient'scircumstances and body weight.

Example 4

A child or adult receiving nutrition parenterally can be treated tosupplement the nutrition formula with a formulation comprising 3 mg ormore of either the purified L-enantiomer or the racemate mixturecomposed of equal proportions of the D- and L-isomers of NACadministered three or four times a day up to the highest tolerable dose,given that there will be individual variability in the ability totolerate NAC, variability in the amount of the cysteine source in thetotal parenteral nutrition formulation and the variability of theconcomitantly administered drugs.

Example 5

A child or adult having liver failure or liver damage or having elevatedliver enzymes and fever who is already compromised can be treated with acold, pain, antipyretic or other formulation comprising between 4 and 10mg/kg acetaminophen and up to 130 mg/kg of either the purifiedL-enantiomer or the racemate mixture composed of equal proportions ofthe D- and L-isomers of NAC administered either serially orco-administered three or four times a day up to the highest tolerabledose given that there will be individual variability in the ability totolerate NAC.

Example 6

A patient having HIV infection can be treated with a formulationcomprising a therapeutically effective amount of AZT as part of amulti-drug antiviral regimen and a toxicity-reducing amount of eitherthe purified L-enantiomer or the racemate mixture composed of equalproportions of the D- and L-isomers of NAC administered either seriallyor co-administered two, three or four times a day up to the highesttolerable dose, given that there will be individual variability in theability to tolerate NAC. It is preferred that NAC be formulated at highdoses as an effervescent tablet or in granular form in a single dosepacket to be dissolved in water to prevent untoward stomach effects.This dosage of NAC is sufficient to decrease key aspects of AZT toxicityin human HIV patients.

Example 7

AZT and NAC can be administered perinatally and neonatally to preventvertical transmission of the HIV virus to the child. Before delivery,the mother is treated with a therapeutically effective amount of AZT anda toxicity-reducing amount of either the purified L-enantiomer or theracemate mixture composed of equal proportions of the D- and L-isomersof NAC administered either serially or co-administered two, three, orfour times a day to the highest tolerable dose, given that there will beindividual variability in the ability to tolerate NAC. Dosage iscontinued to the child after delivery to prevent oxidative stress andother AZT toxicity. It is preferred that NAC be formulated at high dosesas an effervescent tablet or in granular form in a single dose packet tobe dissolved in water to prevent untoward stomach effects. This dosageof NAC is sufficient to decrease key aspects of AZT toxicity in humanHIV patients.

Example 8

A patient with newly-diagnosed or suspected exposure to HIV can betreated with a formulation comprising a therapeutically effective amountof AZT or other similar anti-retroviral drug as normally used and atoxicity-reducing amount of either the purified L-enantiomer or theracemate mixture composed of equal proportions of the D- and L-isomersof NAC administered either serially or co-administered two, three orfour times a day up to the highest tolerable dose, given that there willbe individual variability in the ability to tolerate NAC. It ispreferred that NAC be formulated at high doses as an effervescent tabletor in granular form in a single dose packet to be dissolved in water toprevent untoward stomach effects. This dosage of NAC is sufficient todecrease key aspects of AZT toxicity in human HIV patients.

While the present invention has been described with reference to thespecific embodiments thereof, it should be understood by those skilledin the art that various changes may be made and equivalents may besubstituted without departing from the true spirit and scope of theInvention. In addition, many modifications may be made to adapt aparticular situation, material, composition of matter, process, processstep or steps, to the objective, spirit and scope of the presentinvention. All such modifications are intended to be within the scope ofthe claims appended hereto.

What is claimed is:
 1. A pharmaceutical composition useful for treatingor preventing the toxic effects of therapeutic agents in mammals,comprising a toxicity-reducing amount of N-acetylcysteine or apharmaceutically acceptable salt or derivative thereof alone or incombination with a therapeutic or greater amount of acetaminophen or aderivative thereof, in combination with a pharmaceutically acceptableexcipient or carrier, wherein a unit dose of N-acetylcysteine, incombination with acetaminophen or a derivative thereof, comprises atleast about 1.5 mg/kg and not more than about 2.000 mg.
 2. Apharmaceutical composition according to claim 1 wherein each dosage unitcontains at least about 1 mg N-acetylcysteine or apharmaceutically-acceptable salt or derivative thereof.